Transmission device, transmission method, reception device, and reception method

ABSTRACT

There is provided a transmission device including circuitry configured to generate a physical layer frame. A time information descriptor is included in a preamble of the physical layer frame. The time information descriptor includes a time information flag that indicates presence or absence of time information in the time information descriptor. The circuitry is configured to transmit the physical layer frame including the preamble and a payload. The time information indicates a time of a predetermined position in a stream of the physical layer frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/554,016, filed Aug. 28, 2017, which is a U.S. National PhaseApplication of International Application No. PCT/JP2016/002449, filedMay 19, 2016, which claims the benefit of Japanese Application No.2015-112212, filed Jun. 2, 2015, the entire contents of each of whichare incorporated herein by reference.

TECHNICAL FIELD

The present technology relates to a transmission device, a transmissionmethod, a reception device, and a reception method, and particularly, toa transmission device, a transmission method, a reception device, and areception method capable of efficiently transferring time information.

BACKGROUND ART

For example, in Advanced Television Systems Committee (ATSC) 3.0 whichis one of the next-generation terrestrial broadcast standards, notTransport Stream (TS) packets but User Datagram Protocol (UDP)/InternetProtocol (IP), that is, IP packets including UPD packets, are mainlydecided to be used for data transfer. In the future, IP packets areexpected to be used in broadcast schemes other than ATSC 3.0.

When TS is broadcast, a program clock reference (PCR) is transferred astime information for synchronization between a transmission side and areception side (for example, see NPL 1).

CITATION LIST Non Patent Literature

[NPL 1]

-   “ARIB STD-B44 2.0 Edition,” Association of Radio Industries and    Businesses

SUMMARY Technical Problem

In broadcast schemes such as ATSC 3.0, time information is requested tobe efficiently transferred when the time information for synchronizationbetween a transmission side and a reception side is transferred.

In the present technology, it is desirable to efficiently transfer timeinformation.

Solution to Problem

According to an embodiment of the present disclosure, there is provideda transmission device including circuitry configured to generate aphysical layer frame. A time information descriptor is included in apreamble of the physical layer frame. The time information descriptorincludes a time information flag that indicates presence or absence oftime information in the time information descriptor. The circuitry isconfigured to transmit the physical layer frame including the preambleand a payload. The time information indicates a time of a predeterminedposition in a stream of the physical layer frame.

According to an embodiment of the present disclosure, there is provideda method of a transmission device for transmitting a physical layerframe. The method includes generating, by circuitry of the transmissiondevice, the physical layer frame. A time information descriptor isincluded in a preamble of the physical layer frame. The time informationdescriptor includes a time information flag that indicates presence orabsence of time information in the time information descriptor. Themethod includes transmitting, by the circuitry, the physical layer frameincluding the preamble and a payload. The time information indicates atime of a predetermined position in a stream of the physical layerframe.

According to an embodiment of the present disclosure, there is provideda reception device including circuitry configured to receive a physicallayer frame. A time information descriptor is included in a preamble ofthe physical layer frame. The time information descriptor includes atime information flag that indicates presence or absence of timeinformation in the time information descriptor. The circuitry isconfigured to perform a process based on the time information when thetime information is included in the time information descriptor. Thetime information indicates a time of a predetermined position in astream of the physical layer frame including the preamble and a payload.

According to an embodiment of the present disclosure, there is provideda method of a reception device for receiving a physical layer frame. Themethod includes receiving, by circuitry of the reception device, thephysical layer frame, a time information descriptor is included in apreamble of the physical layer frame. The time information descriptorincludes a time information flag that indicates presence or absence oftime information in the time information descriptor. The method includesperforming a process based on the time information when the timeinformation is included in the time information descriptor. The timeinformation indicates a time of a predetermined position in a stream ofthe physical layer frame including the preamble and a payload.

The transmission device or the reception device may be an independentdevice or an internal block included in one device.

Advantageous Effects of Invention

According to an embodiment of the present technology, it is possible toefficiently transfer time information.

Note that the effects described above are not necessarily limited, andalong with or instead of the effects, any effect that is desired to beintroduced in the present specification or other effects that can beexpected from the present specification may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of anembodiment of a transfer system to which an embodiment of the presenttechnology is applied.

FIG. 2 is a diagram illustrating an example of a protocol stack ofbroadcast performed in the transfer system.

FIG. 3 is a diagram for describing time information.

FIG. 4 is a diagram illustrating the format of an NTP packet.

FIG. 5 is a diagram for describing an example of an arrangement positionof the time information.

FIG. 6 is a diagram for describing a first arrangement example when thetime information is arranged in the head of a payload of a physicallayer frame.

FIG. 7 is a diagram for describing type information of a generic packet.

FIG. 8 is a diagram for describing a second arrangement example when thetime information is arranged in the head of the payload of the physicallayer frame.

FIG. 9 is a diagram for describing a third arrangement example when thetime information is arranged in the head of the payload of the physicallayer frame.

FIG. 10 is a diagram for describing extension type information(EXT_TYPE).

FIG. 11 is a block diagram illustrating a configuration example of atransmission device 10.

FIG. 12 is a flowchart for describing an example of a transmissionprocess performed by the transmission device 10.

FIG. 13 is a block diagram illustrating a configuration example of areception device 20.

FIG. 14 is a flowchart for describing a reception process performed bythe reception device 20.

FIG. 15 is a diagram for describing time information which is defined inthe PTP and can be used as the time information.

FIG. 16 is a diagram for describing an example of a method of reducing atransfer frequency of the PTP.

FIG. 17 is a diagram for describing an example of a method ofcompressing the PTP.

FIG. 18 is a diagram illustrating an example of a compression mode inwhich the PTP is compressed.

FIG. 19 is a diagram illustrating a first example of the syntax of atime information descriptor.

FIG. 20 is a diagram illustrating a second example of the syntax of thetime information descriptor.

FIG. 21 is a diagram illustrating the configuration of a T2 frame(T2frame) which is a physical layer frame of DVB-T.2.

FIG. 22 is a block diagram illustrating a configuration example of anembodiment of a computer to which an embodiment of the presenttechnology is applied.

DESCRIPTION OF EMBODIMENTS

<Transfer System in Embodiment to which the Present Technology isApplied>

FIG. 1 is a block diagram illustrating a configuration example of anembodiment of a transfer system to which the present technology isapplied.

In FIG. 1, the transfer system is configured to include a transmissiondevice 10 and a reception device 20.

The transmission device 10 performs, for example, transmission of aservice such as a program. That is, the transmission device 10 transmits(transfers) a stream of target data, which is a transmission target suchas image or audio data serving as a component included in a service suchas a program (television broadcast program), as a digital broadcastsignal via a transfer path 30.

The reception device 20 receives the digital broadcast signaltransmitted from the transmission device 10 via the transfer path 30,restores the digital broadcast signal to the original stream, andoutputs the original stream. For example, the reception device 20outputs the image or audio data serving as the component included in theservice such as a program.

The transfer system in FIG. 1 can be applied to data transfer whichconforms to Advanced Television Systems Committee Standard (ATSC),Digital Video Broadcasting (DVB), Integrated Services DigitalBroadcasting (ISDB) or other data transfer. As the transfer path 30, aground wave, a satellite channel, a cable television network (wiredcircuit), or the like can be adopted.

<Protocol Stack>

FIG. 2 is a diagram illustrating an example of a protocol stack ofbroadcast performed in the transfer system in FIG. 1.

That is, FIG. 2 illustrates a data structure of data (a packet and aframe) handled in the transfer system in FIG. 1.

In the transfer system, data of a first layer (the physical layer) L1,data of a second layer (the data link layer) L2, and data of a thirdlayer (the network layer) L3 of the Open Systems Interconnection (OSI)reference model are handled.

In FIG. 2, an IP packet (IP Packet) is the data of the third layer L3, ageneric packet (Generic Packet) is the data of the second layer L2, anda BB frame (Baseband Frame), an FEC frame (FEC Frame), and a physicallayer frame (Physical Frame) are the data of the first layer L1.

In the transfer system in FIG. 1, data broadcast is performed using IPpackets.

The IP packet is configured to include an IP header (IP Header) and data(Data). For example, image or audio data is arranged in the data of theIP packet.

In the transmission device 10, a generic packet is configured(generated) from the IP packet.

The generic packet is configured to include a generic header (GenericHeader) and a payload (Payload). One IP packet or a plurality of IPpackets are arranged in the payload of the generic packet.

In the transmission device 10, the BB frame is configured from thegeneric packet.

The BB frame is configured to include a BB header (Baseband FrameHeader) and a payload (Payload). One or a plurality of generic packetsare arranged in the payload of the BB frame.

In the transmission device 10, the BB frame is scrambled in units of oneBB frame or a plurality of BB frames, as necessary, and a parity forerror correction of the physical layer is appended to the BB frame toconfigure an FEC frame.

Further, in the transmission device 10, a process for the physicallayer, such as bit interleaving, mapping to a signal point on aconstellation, or interleaving in a time direction or a frequencydirection, is performed on the FEC frame in units of one FEC frame or aplurality of FEC frames, as necessary. Then, in the transmission device10, a preamble is appended to the FEC frame after the process for thephysical layer to configure a physical layer frame.

That is, the physical layer frame is configured to include the preamble(BS) and the payload (Payload). The FEC frame is arranged in the payloadof the physical layer frame.

In FIG. 2, for example, the physical layer frame has a “bootstrap (BS)”and “Preamble” as the preamble as in the ATSC frame of ATSC 3.0.

Here, “BS” is also referred to as a first preamble BS and “Preamble” isalso referred to as a second preamble Preamble.

The first preamble BS corresponds to, for example, a P1 symbol includedin a T2 frame of DVB-T.2 and the second preamble Preamble correspondsto, for example, a P2 symbol included in the T2 frame.

The payload of the physical layer frame corresponds to, for example, adata symbol included in the T2 frame.

The physical layer frame structure used in DVB-T2 or ATSC 3.0 isconfigured to have a length of, for example, about 100 ms to about 200ms. For the physical layer frame, the subsequent payload can beprocessed after the preamble is processed.

That is, the reception device 20 receives the physical layer frame anddemodulates the preamble of the physical layer frame. Further, thereception device 20 processes the payload of the physical layer frameusing the preamble of the physical layer frame to restore the FEC frame,the BB frame, the generic packet, and the IP packet in this order fromthe physical layer frame.

In the process for the payload of the physical layer frame, the preambleof the physical layer frame is necessary. Therefore, when reception fromthe middle of the physical layer frame starts in the reception device20, the data received after the start of the reception and before thepreamble subsequently appears is discarded.

<Time Information>

FIG. 3 is a diagram for describing time information.

In the transfer system in FIG. 1, as described with reference to FIG. 2,the physical layer frame is configured from the IP packet in thetransmission device 10 and a stream of the physical layer frame istransmitted to the reception device 20.

Time information such as a PCR of the TS is not transmitted in the IPpacket. Therefore, for synchronization between the transmission device10 and the reception device 20, time information is preferably includedin the stream of the physical layer frame.

Accordingly, the transmission device 10 can include time information inthe stream of the physical layer frame.

As illustrated in FIG. 3, the time information can be included in thepreamble of the physical layer frame.

Here, for example, in ATSC 3.0, about 30 bits to about 40 bits areassumed as the first preamble BS of the preamble of the physical layerframe. Accordingly, the first preamble BS may not have a sufficientnumber of bits to include the time information.

Accordingly, the time information can be included in the second preamblePreamble of the preamble of the physical layer frame.

The time information represents an absolute time of a predeterminedposition in the stream of the physical layer frame. A time of thepredetermined position in the stream refers to a time of a predeterminedtiming while a bit at the predetermined position is processed by thetransmission device 10. As the time of the predetermined timing whilethe bit at the predetermined position is processed by the transmissiondevice 10, for example, there is a time of a timing when the bit at thepredetermined position is output from a certain block of thetransmission device 10 or a time of a timing at which the bit at thepredetermined position is processed by a certain block of thetransmission device 10.

Here, the predetermined position in the stream of the physical layerframe at which the time information represents the time is assumed to bea time position.

As the time position, for example, the position of the head of thephysical layer frame (the position of the head of the first preamble BS)which has the preamble including the time information can be adopted.

As the time position, for example, the position of a boundary betweenthe first preamble BS and the second preamble Preamble (the position ofthe end of the first preamble BS) (the position of the head of thesecond preamble Preamble) of the physical layer frame which has thepreamble including the time information can be adopted.

Further, as the time position, for example, the position of the end ofthe second preamble Preamble of the physical layer frame which has thepreamble including the time information can be adopted.

In addition, as the time position, any position in the physical layerframe can be adopted.

In the physical layer frame, a sampling frequency of the first preambleBS can be different from a sampling frequency of a portion after thesecond preamble Preamble. When the sampling frequency of the firstpreamble BS is different from the sampling frequency of the portionafter the second preamble Preamble, the first preamble BS and theportion after the second preamble Preamble are different in a timecounting method. Therefore, when the position of the head of the firstpreamble BS is adopted as the time position, it is necessary to changethe counting method in the first preamble BS and the portion after thesecond preamble Preamble in regard to the counting of the time using thetime position as a reference. In contrast, when the position of the headof the second preamble Preamble is adopted as the time position, it isnot necessary to change the counting method in regard to the counting ofthe time using the time position as a reference, that is, the countingof the time in the portion after the second preamble Preamble.

Accordingly, in FIG. 3, the position of the head of the second preamblePreamble (the position of the boundary between the first preamble BS andthe second preamble Preamble) of the physical layer frame which has thepreamble including the time information is adopted as the time position.

The preamble (the first preamble BS and the second preamble Preamble) ispresent at the fixed position, that is, for example, the head of eachphysical layer, and is necessarily processed first when the physicallayer frame is processed. Accordingly, the reception device 20 caneasily acquire and process the time information included in thepreamble.

Since the preamble is transferred relatively robustly, the timeinformation included in the preamble can also be transferred relativelyrobustly.

Here, as the time information, for example, any time information such astime information defined in the Network Time Protocol (NTP), timeinformation defined in Third Generation Partnership Project (3GPP), timeinformation defined in the Precise Time Protocol (PTP), the timeinformation included in Global Positioning System (GPS) information, orother time information with a uniquely decided format can be adopted.

FIG. 4 is a diagram illustrating the format of an NTP packet.

A 2-bit leap indicator (LI) indicates that a leap second is inserted ordeleted in the 1 final minute of a current month. A 3-bit version number(VN) indicates a version of the NTP. A 3-bit Mode indicates an operationmode of the NTP.

An 8-bit Stratum indicates a layer and an 8-bit Poll indicates aninterval (units of seconds) of continuous NTP messages as a pollinginterval. An 8-bit Precision indicates precision (units of seconds) of asystem clock.

A Root Delay indicates reciprocation delay up to a reference time as aroot delay in the NTP short format. A Root Dispersion indicates adispersion of a total delay up to the reference time in the NTP shortformat. A Reference ID indicates an identifier that represents thereference time. In a broadcast system, “0000” indicating NULL can bestored in the Reference ID.

A Reference Timestamp indicates a time at which a system time is finallycorrected as a reference timestamp in the NTP long format. An OriginTimestamp indicates a time of a client at which a request is transmittedfrom the client to a server as a start timestamp in the NTP long format.In a broadcast system, “0” can be stored in the Origin Timestamp.

A Receive Timestamp indicates a time of the server receiving the requestreceived from the client as a reception timestamp in an NTP long format.In a broadcast system, “0” is stored in the Receive Timestamp. ATransmit Timestamp indicates a time of the server transmitting aresponse to the client as a transmission timestamp in the NTP longformat.

In addition, the NTP packet has an Extension Field 1 or Extension Field2 which is an extension field and a Key Identifier or dgst (messagedigest), as necessary.

As the time information, 64-bit time information represented with thesame format as the timestamp such as the Reference Timestamp of the NTPpacket can be adopted.

Here, in the 64-bit time of the timestamp of the NTP packet, there is aproblem that a time is discontinuous due to the leap second. However,the time information included in the physical layer frame has sufficientgranularity.

In addition to the timestamp of the NTP packet, time information definedin 3GPP, that is, for example, timeInfo-r11 which is time informationdefined in 3GPP TS 36 331, can be adopted as the time information.

The timeInfo-r11 is configured to have 56 bits of a 39-bittimeInfoUTC-r11, a 2-bit dayLightSavingTime-r11, an 8-bitleapSeconds-r11, and a 7-bit localTimeOffset-r11. In the timeInfo-r11,granularity is slightly insufficient for the time information includedin the physical layer frame, but the problem of the leap second does notoccur.

In addition, time information defined with the PTP, that is, 80 bitsrepresenting a time defined in IEEE1588 in regard to a PTP packet can beadopted as the time information. In the 80 bits representing a time ofthe PTP packet, 48 bits of the 80 bits represent a time in units ofseconds and the remaining 32 bits represent a time in units ofnanoseconds. Accordingly, the time information defined in the PTP hassufficient granularity as the time information included in the physicallayer frame, and thus can represent an accurate time. The timeinformation preferably represents a more accurate time from theviewpoint of reproducing an accurate time in the reception device 20.When the time information defined in the PTP is adopted as the timeinformation included in the physical layer frame, the accurate timeinformation can be transferred and the accurate time can be reproducedin the reception device 20. Further, in the time information defined inthe PTP, the problem of the leap second does not occur.

<Arrangement Position of Time Information>

FIG. 5 is a diagram for describing an example of an arrangement positionof the time information.

In FIG. 3, the time information is arranged (included) in the preambleof the physical layer frame. However, the time information can bearranged in, for example, the payload of the physical layer frame otherthan the preamble of the physical layer frame.

In FIG. 5, the time information is arranged in a head portion of thepayload of the physical layer frame.

When the time information is arranged in the head portion of the payloadof the physical layer frame, the reception device 20 can acquire thetime information arranged in the head of the payload after theprocessing of the preamble (the first preamble BS and the secondpreamble Preamble) of the physical layer frame.

<First Arrangement Example when Time Information is Arranged in Payload>

FIG. 6 is a diagram for describing a first arrangement example when thetime information is arranged in the head of the payload of the physicallayer frame.

In the first arrangement example, the time information is arranged inthe payload of the generic packet in the head of the BB frame of thehead of the payload of the physical layer frame as the head of thepayload of the physical layer frame.

FIG. 6 illustrates a configuration example of the generic packet.

In the generic packet in FIG. 6, 3-bit type information (Type) is set inthe head of the generic header. Information regarding the type of dataarranged in the payload of the generic packet is set in this typeinformation.

When the time information and other signaling information for signalingare arranged in the payload of the generic packet, for example, “100” isset in the type information of the generic header. In the genericheader, a subsequent portion of the type information in which “100” isset is considered as a 1-bit reserved region (Res: Reserved) and a 1-bitheader mode (HM: HeaderMode) is subsequently arranged.

When “0” is set as the header mode, 11-bit length information (Length(LSB)) is arranged continuously to follow the header mode. This lengthinformation is set with the length of the payload of the generic packet.In contrast, when “1” set as the header mode, total 16-bit lengthinformation of the 11-bit length information (Length (LSB)) and 5-bitlength information (Length (MSB)) is arranged continuously to follow theheader mode and a 3-bit reserved region (Res) is further provided.

When “0” is set as the header mode, the length information (Length(LSB)) has 11 bits. The 11-bit length information can represent a valueof a range of 0 to 2047 (=2¹¹−1) bytes as the length of the payload ofthe generic packet. However, the 11-bit length information may notrepresent the length of the payload equal to or greater than 2048 bytes.Accordingly, when data equal to or greater than 2048 bytes is arrangedin the payload, “1” is set as the header mode. In this case, 1 byte (8bits) is added as the region of the generic header, and thus the lengthinformation has 16 bits. The 16-bit length information can represent thelength of the payload equal to or greater than 2048 bytes.

In the generic packet, the payload is arranged after the generic headerhaving the above-described configuration. Here, since “100” is set asthe type information of the generic header, signaling informationincluding the time information is arranged in the payload.

FIG. 7 is a diagram for describing type information of the genericpacket in FIG. 6.

When the IP packet of IPv4 is arranged in the payload of the genericpacket, “000” is set in the type information. When the compressed IPpacket is arranged in the payload, “001” is set in the type information.Further, when the TS packet of the MPEG2-TS scheme is arranged in thepayload, “010” is set in the type information.

When the signaling information such as the time information is arrangedin the payload, “100” is set in the type information. In FIG. 7, ternarytype information of “011,” “101,” and “110” is undefined (Reserved).When extension of the type information is insufficient in the ternaryundefined (Reserved), the type information (a region of the typeinformation) can be further extended by setting “111” in the typeinformation.

<Second Arrangement Example when Time Information is Arranged inPayload>

FIG. 8 is a diagram for describing a second arrangement example when thetime information is arranged in the head of the payload of the physicallayer frame.

In the second arrangement example, the time information is arranged inthe header of the generic packet in the head of the BB frame of the headof the payload of the physical layer frame as the head of the payload ofthe physical layer frame.

FIG. 8 illustrates a configuration example of the generic packet.

As described with reference to FIG. 6, in the generic packet, typeinformation regarding the type of data arranged in the payload of thegeneric packet is set in 3-bit type information (Type) of the head ofthe generic header.

In the second arrangement example, “000,” “001,” or “010” is set in the3-bit type information of the generic header.

As described with reference to FIG. 7, when “000” is set as the typeinformation, an IP packet of IPv4 is arranged in the payload. When “001”is set, a compressed IP packet is arranged in the payload. When “101” isset as the type information, a TS packet is arranged in the payload.

In the generic header, 1-bit packet setting information PC (PacketConfiguration) is arranged after the type information in which “000,”“001,” or “010” is set. When “0” is set as the packet settinginformation PC, the generic header enters a normal mode. Then, accordingto the subsequently arranged header mode (HM), 11-bit length information(Length) or 16-bit length information and 3-bit reserved region (Res)are arranged. In the payload continuously following the generic header,an IP packet of IPv4, a compressed IP packet, or a TS packet is arrangedaccording to the type information of the generic header.

In contrast, when “1” is set as the packet setting information PC, thegeneric header enters a signaling mode. Then, according to thesubsequently arranged header mode (HM), the length information (Length)is arranged. That is, when “0” is set as the header mode, 11-bit lengthinformation (Length (LSB)) is arranged continuously to follow the headermode. Further, the generic header extends. Then, signaling information(Signaling) including the time information is arranged after the lengthinformation.

When “1” is set as the packet setting information PC and “1” is set asthe header mode (HM), 16-bit length information (Length) and 3-bitreserved region (Res) are arranged after the header mode. Further, thegeneric header is extended. Then, signaling information (Signaling)including the time information is arranged after the reserved region.

The portion up to the foregoing signaling information is set as thegeneric header (extension header) and the payload is arranged after thegeneric header. In the payload, an IPv4, a compressed IP packet, or thelike is arranged according to the type information of the genericheader.

<Third Arrangement Example when Time Information is Arranged in Payload>

FIG. 9 is a diagram for describing a third arrangement example when thetime information is arranged in the head of the payload of the physicallayer frame.

In the third arrangement example, the time information is arranged inthe BB header of the BB frame in the head of the payload of the physicallayer frame as the head of the payload of the physical layer frame.

FIG. 9 illustrates a configuration example of the BB frame.

In FIG. 9, the BB frame is configured to include the BB header and thepayload (Payload). A 1-byte or 2-byte header (Header) is arranged in theBB header. Further, a 1-byte or 2-byte optional field (Optional Field)and an extension field (Extension Field) are arranged in the BB header.

In the head of the header (Header), a 1-bit mode (MODE) is set.

When “0” is set as the 1-bit mode (MODE), only 7-bit pointer information(Pointer (LSB)) is arranged after the mode in the header. The pointerinformation is information that indicates the position of the genericpacket arranged in the payload of the BB frame. For example, when dataof the generic packet arranged in the end of a certain BB frame isarranged across a subsequent BB frame, position information of thegeneric packet arranged in the head of the subsequent BB frame can beset as the pointer information.

When “1” is set as the mode (MODE), 7-bit pointer information (Pointer(LSB)), 6-bit pointer information (Pointer (MSB)), and a 2-bit optionalflag (OPTI: OPTIONAL) are arranged after the mode in the header. Anoptional field (Optional Field) and an extension field (Extension Field)are arranged in the optional flag that indicates whether the BB headerextends.

When the optional field and the extension field are not extended, “00”is set in the optional flag.

When only the optional field is extended, “01” or “10” is set in theoptional flag. When “01” is set as the optional flag, 1 byte (8 bits) ispadded to the optional field. When “10” is set as the optional flag, 2bytes (16 bits) are padded to the optional field.

When the optional field and the extension field are extended, “11” isset in the optional flag. In this case, 3-bit extension type information(TYPE (EXT_TYPE)) is set in the head of the optional field. In theextension type information, extension length information (EXT_Length)and information regarding the type of the extension field (Extensiontype) arranged after the extension type information are set.

In the third arrangement example, signaling information including thetime information is arranged in the extension field (extension header).

That is, in the third arrangement example, “11” is set as the optionalflag (OPTI), and thus the optional field and the extension field areextended. Further, “011” is set as the extension type information (TYPE(EXT_TYPE)) of the optional field, and thus the signaling informationincluding the time information is arranged in the extension field.

FIG. 10 is a diagram for describing the extension type information (TYPEEXT_TYPE)) in FIG. 9.

In the extension type information, the extension length information(EXT_Length) and the information regarding the type of the extensionfield (Extension type) arranged after the extension type information areset.

That is, when the extension length information (EXT_Length) is arrangedafter the extension type information (EXT_TYPE) and only stuffing bytes(Stuffing Bytes) are arranged in the extension field (Extension Field),“000” is set in the extension type information.

When the extension length information (EXT_Length) is not arranged afterthe extension type information (EXT_TYPE) and an ISSY (Input StreamSynchronization) is arranged in the extension field (Extension Field),“001” is set in the extension type information.

When the extension length information (EXT_Length) is arranged after theextension type information (EXT_TYPE) and stuffing bytes are arrangedalong with the ISSY in the extension field (Extension Field), “010” isset in the extension type information.

When the extension length information (EXT_Length) is arranged after theextension type information (EXT_TYPE) and the signaling informationincluding the time information is arranged in the extension field(Extension Field), “011” is set in the extension type information. Inthis case, whether the stuffing bytes are arranged is arbitrary. In FIG.10, extension type information of “100” to “111” is undefined(reserved).

As described above, the time information can be arranged in the head ofthe payload of the physical layer frame.

<Configuration Example of Transmission Device 10>

FIG. 11 is a block diagram illustrating a configuration example of thetransmission device 10 in FIG. 1.

In FIG. 11, the transmission device 10 includes a time informationacquisition unit 61, a descriptor generation unit 62, a preamblegeneration unit 63, a component acquisition unit 64, an encoder 65, aframe generation unit 66, a transmission unit 67, and an antenna 68.

The time information acquisition unit 61 acquires the time informationand supplies the time information to the descriptor generation unit 62.The time information is acquired in the following manner. That is, whena packet necessary to configure the BB frame arrives at a scheduler (notillustrated), the physical layer frame configured to include the BBframe is obtained from a time t at which the BB frame is generated bythe frame generation unit 66 and a time T of the head of the secondpreamble Preamble of the physical layer frame is obtained. Then, thetime T is supplied as a control signal from the scheduler to the timeinformation acquisition unit 61. The time information can be used forSFN synchronization.

The descriptor generation unit 62 generates a time informationdescriptor including the time information from the time informationacquisition unit 61 and supplies the time information descriptor to thepreamble generation unit 63.

The preamble generation unit 63 generates a preamble (the first preambleBS and the second preamble Preamble) in which the time informationdescriptor from the descriptor generation unit 62 is included in, forexample, the second preamble Preamble and supplies the preamble to theframe generation unit 66.

The component acquisition unit 64 acquires image or audio data as thecomponent included in a service (for example, a program) and suppliesthe image or audio data to the encoder 65.

That is, for example, the component acquisition unit 64 acquirescorresponding content according to a period of broadcast time from astorage site of the previous recorded content or acquires live contentfrom a studio or a location site and supplies the content (data of thecontent) to the encoder 65.

The encoder 65 encodes the image or audio data supplied from thecomponent acquisition unit 64 according to a predetermined encodingscheme and supplies the encoded data to the frame generation unit 66 in,for example, an IP packet format.

The frame generation unit 66 generates (configures) the physical layerframe appropriately using the preamble from the preamble generation unit63 and the IP packet from the encoder 64 and supplies the physical layerframe to the transmission unit 67.

That is, as described with reference to FIG. 2, the frame generationunit 66 configures the generic packet in which the IP packet from theencoder 65 is arranged. Further, the frame generation unit 66 configuresthe BB frame in which the generic packet is arranged in the payloads ofthe BB frame.

The frame generation unit 66 configures the FEC frame from the BB frame,performs a necessary process, and arranges the FEC frame in the payloadof the physical layer frame.

Then, the frame generation unit 66 configures the physical layer frameby appending the preamble from the preamble generation unit 63 to thepayload of the physical layer frame and supplies the physical layerframe to the transmission unit 67.

The transmission unit 67 performs a process such as digital modulationor up-converting on the physical layer frame from the frame generationunit 66 and transmits the physical layer frame as a digital broadcastsignal via the antenna 68.

In the transmission device 10 in FIG. 11, it is not necessary tophysically arrange all of the functional blocks in a single device. Atleast some of the functional blocks may be configured as a devicephysically independent from the other functional blocks.

<Transmission Process>

FIG. 12 is a flowchart for describing an example of a transmissionprocess performed by the transmission device 10 in FIG. 11.

In step S11, the time information acquisition unit 61 acquires the timeinformation and supplies the time information to the descriptorgeneration unit 62. Then, the process proceeds to step S12.

In step S12, the descriptor generation unit 62 generates the timeinformation descriptor including the time information from the timeinformation acquisition unit 61, as necessary, and supplies the timeinformation descriptor to the preamble generation unit 63. Then, theprocess proceeds to step S13.

In step S13, the preamble generation unit 63 generates the preamble ofthe physical layer frame in which the time information descriptor fromthe descriptor generation unit 62 is included in the second preamblePreamble and supplies the preamble to the frame generation unit 66.Then, the process proceeds to step S14.

In step S14, the component acquisition unit 64 acquires the image oraudio data as the component configuring the service and supplies theimage or audio data to the encoder 65.

The encoder 65 performs a process such as encoding on the image or audiodata supplied from the component acquisition unit 64 and supplies theimage or audio data to the frame generation unit 66 in the IP packetformat. Then, the process proceeds from step S14 to step S15.

In step S15, the frame generation unit 66 generates the physical layerframe appropriately using the preamble from the preamble generation unit63 and the IP packet from the encoder 64 and supplies the physical layerframe to the transmission unit 67. Then, the process proceeds to stepS16.

In step S16, the transmission unit 67 transmits the physical layer framefrom the frame generation unit 66 as the digital broadcast signal viathe antenna 68.

<Configuration Example of Reception Device 20>

FIG. 13 is a block diagram illustrating a configuration example of thereception device 20 in FIG. 1.

In FIG. 13, the reception device 20 is configured to include an antenna71, a tuner 72, a demodulation unit 73, a processing unit 74, a displayunit 75, and a speaker 76.

The antenna 71 receives the digital broadcast signal from thetransmission device 10 and supplies the digital broadcast signal to thetuner 72.

The tuner 72 is tuned to a component of a predetermined frequencychannel from the digital broadcast signal from the antenna 71 to receivethe physical layer frame transmitted at the frequency channel, andsupplies the physical layer frame to the demodulation unit 73.

The demodulation unit 73 performs a demodulation process on the physicallayer frame supplied from the tuner 72.

That is, the demodulation unit 73 demodulates the preamble (the firstpreamble BS and the second preamble Preamble) of the physical layerframe and further demodulates the payload of the physical layer frameusing the demodulation result of the preamble as necessary.

The demodulation unit 73 demodulates (decodes) the FEC frame obtained bydemodulating the payload of the physical layer frame.

Then, the demodulation unit 73 demodulates the generic packet from theBB frame obtained as the demodulation result of the FEC frame,demodulates the IP packet from the generic packet, and supplies the IPpacket to the processing unit 74.

The demodulation unit 73 acquires the time information descriptorincluded in the preamble of the physical layer frame in the demodulationprocess and supplies the time information descriptor to the processingunit 74.

The processing unit 74 decodes an image and audio of a program from theIP packet from the demodulation unit 73, supplies the image to thedisplay unit 75, and supplies the audio to the speaker 76.

The processing unit 74 includes a time information acquisition unit 81.The time information acquisition unit 81 acquires the time informationfrom the time information descriptor from the demodulation unit 73 asnecessary. The processing unit 74 performs a necessary process using thetime information acquired from the time information acquisition unit 81.

That is, the processing unit 74 (or the demodulation unit 73) performs,for example, clock data recovery using the time information and performsa synchronization process or the like for synchronization with thetransmission device 10. The processing unit 74 performs a timing controlprocess of controlling a timing of presentation of the image, the audio,and the like using the time information. In addition, for example, thetime information can be applied to synchronization such as SFNsynchronization of DVB-T.2.

The display unit 75 displays the image from the processing unit 74. Thespeaker 76 outputs the audio from the processing unit 74.

In the reception device 20 in FIG. 13, the configuration in which thedisplay unit 75 and the speaker 76 are internally included has beendescribed, but the display unit 75 and the speaker 76 may be providedexternally.

<Reception Process>

FIG. 14 is a flowchart for describing a reception process performed bythe reception device 20 in FIG. 13.

In step S21, the tuner 72 receives the physical layer frame from thedigital broadcast signal from the antenna 71 and supplies the physicallayer frame to the demodulation unit 73. Then, the process proceeds tostep S22.

In step S22, the demodulation unit 73 performs the demodulation processon the physical layer frame supplied from the tuner 72 and supplies theIP packet or the time information descriptor obtained as the result tothe processing unit 74. Then, the process proceeds to step S23.

In step S23, the time information acquisition unit 81 of the processingunit 74 acquires the time information from the time informationdescriptor from the demodulation unit 73. Then, the process proceeds tostep S24. Here, the processing unit 74 performs a synchronizationprocess or the like for synchronization with the transmission device 10using the time information acquired by the time information acquisitionunit 81.

In step S24, the processing unit 74 processes the component included inthe IP packet from the demodulation unit 73 in the state of thesynchronization with the transmission device 10. That is, the processingunit 74 decodes the image and the audio of the program from the IPpacket from the demodulation unit 73, supplies the image to the displayunit 75 to display the image, and supplies the audio to the speaker 76to output the audio.

As described above, in the transfer system in FIG. 1, the transmissiondevice 10 includes the time information (the time information descriptorincluding the time information) in the preamble of the physical layerframe to transmit the time information. Therefore, the time informationcan be efficiently transferred.

Further, in the transfer system in FIG. 1, the reception device 20performs the process using the time information (which is included inthe time information descriptor) included in the preamble of thephysical layer frame. Therefore, the process can be performed quickly.

<PTP>

FIG. 15 is a diagram for describing time information which can be usedas the time information and is defined in the PTP (hereinafter simplyreferred to as PTP).

The PTP is defined in IEEE1588 and is configured to have 80 bits.

The 80-bit PTP is configured to include a 48-bit second field(secondsField) representing a time in units of seconds and a 32-bitnanosecond field (nanosecondsField) representing a time in units ofnanoseconds.

In the second field, 1 represents 1 second. In the nanosecond field, 1represents 1 nanosecond.

Accordingly, for example, in the PTP representing+2.000000001 seconds,the second field has 0x000000000002 and the nanosecond field has0x00000001. Further, 0x represents that subsequently continuous valuesare hexadecimal numbers.

Here, since 10⁹ nanoseconds are 1 second, the nanosecond field takesvalues from 0 to a value less than 10⁹.

That is, the maximum value of the nanosecond field is 10⁹−1. Since 10⁹−1can be expressed in 30 bits, the 2 high-order bits of the 32-bitnanosecond field are normally 0.

In IEEE 1588, 0:00 on 1 Jan. 1970 in International Atomic Time (TAI) isdefined as an epoch which is a starting point of a time represented bythe PTP. That is, the PTP of IEEE1588 represents a time at which 0:00 on1 Jan. 1970 of TAI is assumed to be the epoch.

As described with reference to FIG. 4, when the PTP is adopted as thetime information included in the physical layer frame, the accurate timeinformation can be transferred and the accurate time can be reproducedin the reception device 10. Thus, it is possible to prevent the problemof the leap second from occurring.

Incidentally, a very accurate time can be expressed according to thePTP. However, when broadcast is performed with the transfer system inFIG. 1, transferring of the time information with high precisionexcessive for the broadcast may result in oppression of a transferbandwidth, and thus is not efficient.

The 80-bit PTP is the time information with considerably sufficientprecision in the supply of the service by broadcast. Even when aninformation amount of the PTP is reduced to some extent, the supply ofthe service by broadcast can be sufficiently maintained.

Accordingly, in the transfer system in FIG. 1, the information amount ofthe PTP which is the time information can be reduced to be transferred.

As a method of reducing the information amount of the PTP, for example,there is a method of reducing a transfer frequency of the PTP or amethod of compressing the PTP.

Here, as described with reference to FIGS. 5 to 10, the time informationcan be included in the payload rather than the preamble of the physicallayer frame.

However, a case in which the time information is included in thepreamble of the physical layer frame will be exemplified in thefollowing description.

<Method of Reducing Transfer Frequency PTP>

FIG. 16 is a diagram for describing an example of a method of reducing atransfer frequency of the PTP.

The PTP which is the time information can be included in all of thephysical layer frames. For precision necessary for in thesynchronization with the transmission device 10 in the reception device20, it is not necessary to include the PTP in the frames (the secondpreamble Preamble) of all the physical layer frames in some cases.

Accordingly, the PTP are not included in all of the physical layerframes, but can be included in some of the physical layer frames.Accordingly, it is possible to reduce the transfer frequency of the PTP.

In FIG. 16, the PTP which is the time information is inserted into onlythe head physical layer frame (the second preamble Preamble of thephysical layer frame) among the four physical layer frames at intervalsof the four physical layer frames to be transferred.

In this case, the information amount of the PTP transferred from thetransmission device 10 to the reception device 20 can be reduced toabout ¼, and thus it is possible to efficiently transfer the PTP.

<Method of Compressing PTP>

FIG. 17 is a diagram for describing an example of a method ofcompressing the PTP.

According to the 48-bit second field of the PTP, considerable times ofabout 892 million years can be expressed. However, in broadcast, suchextensive times are not necessary.

Here, for example, in the USA, the analog broadcast was switched to thefirst-generation digital broadcast scheme (ATSC) in 1980. Further, thefirst-generation digital broadcast scheme (ATSC) is expected to beswitched to the second-generation digital broadcast scheme (ATSC3.0) ofabout 30 years from the broadcast start.

In view of this situation, when the broadcast by the transfer system inFIG. 1 is assumed to be used for, for example, about 90 years from 2016,the time information included in the physical layer frame suffices forcounting times up to about 2106.

The epoch defined as the epoch of PTP in IEEE1588 (hereinafter alsoreferred to as a standard epoch) is 1970 (0:00 on 1 January). Therefore,when times up to 2106 are counted, times of 136 years=2106-1970 may becounted.

The number of seconds in 136 years can be counted with 32 bits. When thetimes up to 2106 are counted with the PTP, 32 bits suffice for thesecond field.

When a uniquely decided epoch (hereinafter also referred to as a uniqueepoch) is adopted as the epoch of the PTP rather than the standardepoch, a small number of bits can be further adopted as the secondfield.

That is, for example, when seconds are counted with 31 bits, the numberof seconds of about 68 years can be counted. Now, for example, when 2016is assumed to be used as a unique epoch and 31 bits are adopted as thesecond field, times up to 2084=2016+68 can be counted.

Accordingly, for example, when the broadcast by the transfer system inFIG. 1 is assumed to be used from 2016 to about 2080, 31 bits can beadopted as the second field by using 2016 (1 January) as the uniqueepoch.

Here, the foregoing description can be summarized as follows.

That is, when 32 bits are adopted as the second field, the number ofseconds in about 136 years can be counted. According to the secondfield, when the standard epoch is adopted, times up to 2106 (=1970+136)can be counted. When 2016 is adopted as the unique epoch, times up to2152 (=2016+136) can be counted.

When 31 bits are adopted as the second field, the number of seconds inabout 68 years can be counted. According to the second field, when thestandard epoch is adopted, times up to 2038 (=1970+68) can be counted.When 2016 is adopted as the unique epoch, times up to 2084 (=2016+68)can be counted.

How long a period continues has been estimated above as the period inwhich the broadcast is performed in the transfer system in FIG. 1. Forexample, about 31 bits or 32 bits are expected to suffice for the secondfield.

On the other hand, the nanosecond field of the PTP represents a time inunits of nanoseconds. Therefore, a clock of 1 GHz (frequency of 1 GHz)can be counted maximally. However, that high-speed clock (count of theclock) is not necessary for the broadcast.

Here, according to the 32-bit nanosecond field, the clock of 1 GHz canbe counted. That is, according to the 32-bit nanosecond field, values of0x0 to 0x3b9ac9ff (=10⁹−1) are repeatedly counted while increasing avalue of 2° corresponding to 1 ns (=1/(1 GHz)) in synchronization withthe clock of 1 GHz.

For example, according to a 27-bit nanosecond field in which 5 low-orderbits of the 32-bit nanosecond field are deleted, a clock of 32.25 MHz=1GHz/2⁵ can be counted. That is, according to the 27-bit nanosecondfield, in 32-bit conversion, values of 0x0 to 0x3b9ac9e0 (=10⁹−2⁵) arerepeatedly counted while increasing a value of 2⁵ corresponding to 2⁵ ns(=1/(32.25 MHz)) in synchronization with the clock of 32.25 MHz.

Further, for example, according to a 19-bit nanosecond field in which 13low-order bits of the 32-bit nanosecond field are deleted, a clock of122.0 kHz=1 GHz/213 can be counted. That is, according to the 19-bitnanosecond field, in 32-bit conversion, values of 0x0 to 0x3b9aa000(=10⁹−2¹³) are repeatedly counted while increasing a value of 2¹³corresponding to 2¹³ ns (=1/(122.0 kHz)) in synchronization with theclock of 122.0 kHz.

In the broadcast, a clock of about 90 kHz or about 27 MHz is generallyadopted.

According to the 27-bit nanosecond field in which the clock of 32.25 MHzcan be counted, precision of a clock of 27 MHz can be ensured. Accordingto the 19-bit nanosecond field in which the clock of 122.0 kHz can becounted, precision of a clock of 90 kHz can be ensured.

Accordingly, in the broadcast in which the clock of about 90 kHz orabout 27 MHz is adopted, for example, the 5 or 13 low-order bits aredeleted in the nanosecond field. Thus, sufficient precision can beensured even with 27 bits or 19 bits.

As described with reference to FIG. 15, since the 2 high-order bits ofthe nanosecond field are normally 0, the 27-bit or 19-bit nanosecondfield in which the 5 low-order bits or 13 low-order bits are deleted canbe set as a 25-bit or 17-bit nanosecond field in which the 2 high-orderbits are further deleted.

FIG. 17 illustrates an example of compression of PTP when the secondfield is compressed into 32 bits and the nanosecond field is compressedinto 19 bits.

In the transmission device 10 (see FIG. 11), the 80-bit PTP configuredto include the 48-bit second field and the 32-bit nanosecond field issupplied from the time information acquisition unit 61 to the descriptorgeneration unit 62.

The descriptor generation unit 62 compresses the 48-bit second field toa 32-bit second field (hereinafter also referred to as a compressedsecond field), for example, by deleting the 16 high-order bits in the48-bit second field.

Further, the descriptor generation unit 62 compresses the 32-bitnanosecond field to a 19-bit nanosecond field (hereinafter also referredto as a compressed nanosecond field), for example, by deleting the 13low-order bits in the 32-bit nanosecond field.

The descriptor generation unit 62 includes a 51-bit PTP (hereinafteralso referred to as a compressed PTP) compressed with the 32-bitcompressed second field and the 19-bit compressed nanosecond field inthe time information descriptor to supply the compressed PTP to thepreamble generation unit 63 (see FIG. 11).

In this way, in the method of compressing the PTP, some of the bits ineach of the second field and the nanosecond field of the PTP aredeleted, so that the PTP is compressed into a compressed PTP (compressedtime information) with a so-called intermediate format to betransferred.

In the reception device 20 (see FIG. 13), the time informationacquisition unit 81 acquires the compressed PTP included in the timeinformation descriptor and restores the compressed PTP to the PTP withthe format defined in IEEE1588.

That is, the time information acquisition unit 81 restores the 32-bitcompressed second field to the 48-bit second field by appending (adding)16 bits of zeros bits as the high-order bits of the 32-bit compressedsecond field of the compressed PTP.

Further, the time information acquisition unit 81 restores the 19-bitcompressed nanosecond field to the 32-bit nanosecond field by appending0 of 13 bits as the low-order bits of the 19-bit compressed nanosecondfield of the compressed PTP.

The time information acquisition unit 81 restores the PTP with theformat defined in IEEE1588 configured to include the 48-bit second fieldand the 32-bit nanosecond field.

The descriptor generation unit 62 can compress the 32-bit nanosecondfield to the 17-bit compressed nanosecond field by deleting the 13low-order bits of the 32-bit nanosecond field and deleting the 2high-order bits which are normally 0, as described above.

In this case, the time information acquisition unit 81 restores the17-bit compressed nanosecond field to the 32-bit nanosecond field byappending 0 of 13 bits as the low-order bits of the 17-bit compressednanosecond field and appending 0 of 2 bits as the high-order bits.

When the unique epoch is adopted as the epoch of the PTP rather than thestandard epoch, the descriptor generation unit 62 subtracts a timecorresponding to a difference (hereinafter also referred to as adifference time) between the standard epoch and the unique epoch (uniqueepoch-standard epoch) from the PTP, and then compresses the PTP afterthe subtraction to the compressed PTP.

Further, in this case, the time information acquisition unit 81 restoresthe compressed second field and the compressed nanosecond field to thesecond field and the nanosecond field, and subsequently adds thedifference time to the restored second field and nanosecond field torestore the PTP with the format defined in IEEE1588 (the PTP of thestandard epoch).

<Compression Mode>

FIG. 18 is a diagram illustrating an example of a compression mode inwhich the PTP is compressed.

In FIG. 18, the compression mode is expressed with 4 bits, and 16 kindsof compression modes from mode 0 to mode 15 can be defined.

In FIG. 18, mode 3 and mode 7 to mode 15 are undefined (Reserved). Inpractice, 6 kinds of compression modes are defined.

In mode 0, the PTP is not compressed and is configured to include the48-bit second field and the 32-bit nanosecond field is used as the PTP.In mode 0, the standard epoch is used as the epoch of the PTP.

In mode 1, the 48-bit second field is compressed into the 32-bit secondfield by deleting the 16 high-order bits and the 32-bit nanosecond fieldis compressed into the 19-bit nanosecond field by deleting the 13low-order bits. In mode 1, the standard epoch is used as the epoch ofthe PTP.

In mode 2, the 48-bit second field is compressed into the 32-bit secondfield by deleting the 16 high-order bits and the 32-bit nanosecond fieldis compressed into the 27-bit nanosecond field by deleting the 5low-order bits. In mode 2, the standard epoch is used as the epoch ofthe PTP.

In mode 4, the PTP is not compressed and the PTP configured to includethe 48-bit second field and the 32-bit nanosecond field is used. In mode4, the unique epoch is used as the epoch of the PTP.

In mode 5, the 48-bit second field is compressed into the 32-bit secondfield by deleting the 17 high-order bits and the 31-bit nanosecond fieldis compressed into the 19-bit nanosecond field by deleting the 13low-order bits. In mode 5, the unique epoch is used as the epoch of thePTP.

In mode 6, the 48-bit second field is compressed into the 32-bit secondfield by deleting the 17 high-order bits and the 31-bit nanosecond fieldis compressed into the 27-bit nanosecond field by deleting the 5low-order bits. In mode 6, the unique epoch is used as the epoch of thePTP.

The compression mode is decided, for example, by estimating the numberof bits necessary for the broadcast in the second field and thenanosecond field on the side of the transmission device 10.

As described with reference to FIG. 17, in addition to the low-orderbits, the 2 high-order bits are deleted, so that the nanosecond fieldcan be compressed.

The compression mode in which the low-order bits and the 2 high-orderbits of the nanosecond field are deleted can be allocated to one of theundefined modes in FIG. 18.

<Syntax of Time Information Descriptor>

FIG. 19 is a diagram illustrating a first example of the syntax of atime information descriptor.

In FIG. 19, time_info_flag is a time information flag that indicatespresence or absence of the PTP (compressed PTP) which is the timeinformation. A value 0 indicates that the PTP is present and a value 1indicates that the PTP is not present.

In the embodiment, a 1-bit flag is used as time_info_flag, but 2 bits ormore can be allocated to time_info_flag.

When time_info_flag is 0, the PTP is not included in the timeinformation descriptor. When time_info_flag is 1, the PTP is included inthe time information descriptor.

For example, as illustrated in FIG. 16, when the PTP is inserted intoonly the head physical layer frame among the four physical layer framesat intervals of the four physical layer frames, 1 is set totime_info_flag of the time information descriptor included in the headphysical layer frame and 0 is set in time_info_flag of the timeinformation descriptor included in the 3 remaining physical layerframes.

In FIG. 19, PTP_secondsField represents the second field of the PTP andPTP_nanosecondsField represents the nanosecond field of the PTP.

In FIG. 19, the compressed PTP in which the compression mode (see FIG.18) is mode 1 is adopted. Therefore, PTP_secondsField has 32 bits andPTP_nanosecondsField has 19 bits.

The syntax in FIG. 19 is used when the compression mode is fixed to apredetermined mode such as mode 1.

The compression mode can be fixed to a mode other than mode 1. A mode towhich the compression mode is fixed can be defined by, for example, abroadcast standard.

FIG. 20 is a diagram illustrating a second example of the syntax of thetime information descriptor.

In FIG. 20, time_info_flag is the time information flag described withreference to FIG. 19.

In FIG. 20, when time_info_flag is 0, the compression mode and the PTPare not included in the time information descriptor. When time_info_flagis 1, the compression mode and the PTP are included in the timeinformation descriptor.

In FIG. 20, mode represents the compression mode.

When mode is 0 or 4, the PTP configured to include the 48-bit secondfield (PTP_secondsField) and the 32-bit nanosecond field(PTP_nanosecondsField) is included in the time information descriptor,as described with reference to FIG. 18.

When mode is 1, the PTP configured to include the 32-bit compressedsecond field (PTP_secondsField) and the 19-bit compressed nanosecondfield (PTP_nanosecondsField) is included in the time informationdescriptor, as described with reference to FIG. 18.

When mode is 2, the PTP configured to include the 32-bit compressedsecond field (PTP_secondsField) and the 27-bit compressed nanosecondfield (PTP_nanosecondsField) is included in the time informationdescriptor, as described with reference to FIG. 18.

When mode is 5, the PTP configured to include the 31-bit compressedsecond field (PTP_secondsField) and the 19-bit compressed nanosecondfield (PTP_nanosecondsField) is included in the time informationdescriptor, as described with reference to FIG. 18.

When mode is 6, the PTP configured to include the 31-bit compressedsecond field (PTP_secondsField) and the 27-bit compressed nanosecondfield (PTP_nanosecondsField) is included in the time informationdescriptor, as described with reference to FIG. 18.

The syntax in FIG. 20 is used when the compression mode can be selected,as necessary.

The time information descriptors in FIGS. 19 and 20 can be configurednot to include time_info_flag which is the time information flag.

When time_info_flag is not included in the time information descriptor,the (compressed) PTP which is the time information is transferred withall of the physical layer frames.

Here, as described above, the method of reducing the transfer frequencyof the PTP or the method of compressing the PTP can be applied not onlyto the PTP which is the time information but also to any timeinformation such as time information defined in the NTP, timeinformation defined in 3GPP, the time information included in GPSinformation, and time information with a uniquely decided format.

As described above, the IP packet is transferred in the transfer systemin FIG. 1. However, for example, a TS packet other than the IP packetcan be transferred.

The transfer system in FIG. 1 can be applied to, for example, any datatransfer of ATSC 3.0, DVB, or ISDB.

<Physical Layer Frame of DVB-T.2>

FIG. 21 is a diagram illustrating the configuration of a T2 frame(T2frame) which is a physical layer frame of DVB-T.2.

The T2 frame includes P1 and P2 serving as a preamble and a data symbol(Data Symbols) serving as a payload.

P1 includes P1 signaling, and P2 includes L1-pre signaling and L1-postsignaling.

L1-post signaling includes Configurable, Dynamic, Extension, CRC, and L1padding.

The time information descriptor can be included in the preamble (forexample, P2 of the preamble) of the T2 frame described above.

<Description of Computer to which the Present Technology is Applied>

Next, the series of processes of the transmission device 10 or thereception device 20 can be performed by hardware or may also beperformed by software. When the series of processes is performed bysoftware, a program configuring the software is installed in a computer.

Thus, FIG. 22 is a block diagram illustrating a configuration example ofan embodiment of a computer in which a program executing theabove-described series of processes is installed.

The program can be recorded in advance in a ROM 103 or a hard disk 105serving as a recording medium internally included in the computer.

Alternatively, the program can be stored (recorded) in a removablerecording medium 111. The removable recording medium 111 can be providedas so-called package software. Here, examples of the removable recordingmedium 111 include a flexible disk, a compact disc read-only memory(CD-ROM) disc, a magneto-optical (MO) disc, a digital versatile disc(DVD), a magnetic disk, and a semiconductor memory.

The program can be installed in the computer from the above-describedremovable recording medium 111 and can also be downloaded to thecomputer via a communication network or a broadcasting network andinstalled in the internally included hard disk 105. That is, forexample, the program can be transferred in a wireless manner from adownload site to the computer via a digital satellite broadcastingartificial satellite or can be transferred in a wired manner from adownload site to the computer via a network such as a local area network(LAN) or the Internet.

The computer internally includes a central processing unit (CPU) 102. Aninput and output interface 110 is connected to the CPU 102 via a bus101.

When a user inputs an instruction by manipulating an input unit 107 viathe input and output interface 110, the CPU 102 accordingly executes theprogram stored in the read-only memory (ROM) 103. Alternatively, the CPU102 loads the program stored in the hard disk 105 to a random accessmemory (RAM) 104 and executes the program.

Thus, the CPU 102 performs a process according to the above-describedflowchart or a process performed by the configuration of theabove-described block diagram. Then, for example, the CPU 102 outputsthe processing result from an output unit 106, transmits the processingunit from a communication unit 108, or records the processing result inthe hard disk 105 via the input and output interface 110 as necessary.

The input unit 107 is configured to include a keyboard, a mouse, and amicrophone. The output unit 106 is configured to include a liquidcrystal display (LCD) or a speaker.

Processing performed herein by the computer according to a program doesnot necessarily have to be performed chronologically in the orderdescribed in a flow chart. That is, processing performed by the computeraccording to a program also includes processing performed in parallel orindividually (for example, parallel processing or processing by anobject).

The program may be processed by one computer (processor) or by aplurality of computers in a distributed manner. Further, the program maybe performed after being transferred to a remote computer.

Further, in the present specification, a system has the meaning of a setof a plurality of configured elements (such as an apparatus or a module(part)), and does not take into account whether or not all theconfigured elements are in the same casing.

Therefore, the system may be either a plurality of apparatuses, storedin separate casings and connected through a network, or a plurality ofmodules within a single casing.

An embodiment of the disclosure is not limited to the embodimentsdescribed above, and various changes and modifications may be madewithout departing from the scope of the disclosure.

For example, the present technology can adopt a configuration of cloudcomputing which processes by allocating and connecting one function by aplurality of apparatuses through a network.

Further, each step described by the above mentioned flow charts can beexecuted by one apparatus or by allocating a plurality of apparatuses.

In addition, in the case where a plurality of processes is included inone step, the plurality of processes included in this one step can beexecuted by one apparatus or by allocating a plurality of apparatuses.

In addition, the effects described in the present specification are notlimiting but are merely examples, and there may be additional effects.

Additionally, the present technology may also be configured as below.

(1)

A transmission device including:

circuitry configured to

generate a physical layer frame, a time information descriptor isincluded in a preamble of the physical layer frame, the time informationdescriptor including a time information flag that indicates presence orabsence of time information in the time information descriptor; and

transmit the physical layer frame including the preamble and a payload,wherein the time information indicates a time of a predeterminedposition in a stream of the physical layer frame.

(2)

The transmission device according to (1),

wherein the time information included in the time information descriptoris compressed.

(3)

The transmission device according to (2),

wherein at least one low-order bit of the time information is deleted togenerate the compressed time information.

(4)

The transmission device according to (2) or (3),

wherein at least one high-order bit of the time information, having avalue of 0, is deleted to generate the compressed time information.

(5)

The transmission device according to any of (2) to (4),

wherein the time information descriptor further includes a compressionmode of the compressed time information.

(6)

The transmission device according to any of (1) to (5),

wherein the preamble includes a first preamble and a second preambleadjacent to the first preamble,

wherein the time information descriptor is included in the secondpreamble, and

wherein the time information included in the time information descriptorindicates the time of a position of a head of the second preamble.

(7)

The transmission device according to any of (2) to (6),

wherein the time information is defined in Network Time Protocol (NTP),Third Generation Partnership Project (3GPP), or Precise Time Protocol(PTP).

(8)

The transmission device according to (7),

wherein, in a 48-bit second field and a 32-bit nanosecond field includedin the time information defined in the PTP, at least one high-order bitof the second field in the time information is deleted and at least onelow-order bit of the nanosecond field in in time information is deletedto generate the compressed time information.

(9)

The transmission device according to (8),

wherein 2 high-order bits of the nanosecond field in the timeinformation are further deleted to generate the compressed timeinformation.

(10)

A method of a transmission device for transmitting a physical layerframe, the method including:

generating, by circuitry of the transmission device, the physical layerframe, a time information descriptor is included in a preamble of thephysical layer frame, the time information descriptor including a timeinformation flag that indicates presence or absence of time informationin the time information descriptor; and

transmitting, by the circuitry, the physical layer frame including thepreamble and a payload, wherein

the time information indicates a time of a predetermined position in astream of the physical layer frame.

(11)

A reception device including:

circuitry configured to

receive a physical layer frame, a time information descriptor isincluded in a preamble of the physical layer frame, the time informationdescriptor including a time information flag that indicates presence orabsence of time information in the time information descriptor; and

perform a process based on the time information when the timeinformation is included in the time information descriptor, wherein

the time information indicates a time of a predetermined position in astream of the physical layer frame including the preamble and a payload.

(12)

The reception device according to (11),

wherein the time information included in the time information descriptoris compressed.

(13)

The reception device according to (12),

wherein at least one low-order bit of the time information is deleted togenerate the compressed time information.

(14)

The reception device according to (12) or (13),

wherein at least one high-order bit of the time information, having avalue of 0, is deleted to generate the compressed time information.

(15)

The reception device according to any of (12) to (14),

wherein the time information descriptor further includes a compressionmode of the compressed time information.

(16)

The reception device according to any of (11) to (15),

wherein the preamble has a first preamble and a second preamble adjacentto the first preamble,

wherein the time information descriptor is included in the secondpreamble, and

wherein the time information included in the time information descriptorindicates the time of a position of a head of the second preamble.

(17)

The reception device according to any of (12) to (16),

wherein the time information is defined in Network Time Protocol (NTP),Third

Generation Partnership Project (3GPP), or Precise Time Protocol (PTP).

(18)

The reception device according to (17),

wherein, in a 48-bit second field and a 32-bit nanosecond field includedin the time information defined in the PTP, at least one high-order bitof the second field is deleted and at least one low-order bit of thenanosecond field is deleted, in a manner wherein, in a 48-bit secondfield and a 32-bit nanosecond field included in the time informationdefined in the PTP, at least one high-order bit of the second field inthe time information is deleted and at least one low-order bit of thenanosecond field in the time information is deleted to generate thecompressed time information

(19)

The reception device according to (18),

wherein 2 high-order bits of the nanosecond field in the timeinformation are further deleted to generate the compressed timeinformation.

(20)

A method of a reception device for receiving a physical layer frame, themethod including:

receiving, by circuitry of the reception device, the physical layerframe, a time information descriptor is included in a preamble of thephysical layer frame, the time information descriptor including a timeinformation flag that indicates presence or absence of time informationin the time information descriptor; and

performing a process based on the time information when the timeinformation is included in the time information descriptor, wherein

the time information indicates a time of a predetermined position in astream of the physical layer frame including the preamble and a payload.

(21)

A transmission device including:

a generation unit configured to generate a physical layer frame in whicha time information descriptor, which includes a time information flagwhich indicates presence or absence of time information indicating atime of a predetermined position in a stream of the physical layer framehaving a preamble and a payload and further includes the timeinformation when the time information flag indicates the presence of thetime information, is included in the preamble; and

a transmission unit configured to transmit the physical layer frame.

(22)

The transmission device according to (21),

wherein the time information descriptor includes compressed timeinformation in which the time information is compressed.

(23)

The transmission device according to (22),

wherein at least one low-order bit of the time information is deleted,in a manner that the time information is compressed into the compressedtime information.

(24)

The transmission device according to (22) or (23),

wherein at least one high-order bit of the time information, thehigh-order bit having a value of 0, is deleted, in a manner that thetime information is compressed into the compressed time information.

(25)

The transmission device according to any of (22) to (24),

wherein the time information descriptor further includes a compressionmode of the time information.

(26)

The transmission device according to any of (21) to (25),

wherein the preamble has a first preamble and a second preamblecontinuously following the first preamble,

wherein the time information descriptor is included in the secondpreamble, and

wherein the time information included in the time information descriptorindicates a time of a position of a head of the second preamble.

(27)

The transmission device according to any of (22) to (26),

wherein the time information is time information defined in Network TimeProtocol (NTP), time information defined in Third Generation PartnershipProject (3GPP), or time information defined in Precise Time Protocol(PTP).

(28)

The transmission device according to (27),

wherein, in a 48-bit second field and a 32-bit nanosecond field includedin the time information defined in the PTP, at least one high-order bitof the second field is deleted and at least one low-order bit of thenanosecond field is deleted, in a manner that the time information iscompressed into the compressed time information.

(29)

The transmission device according to (28),

wherein 2 high-order bits of the nanosecond field are further deleted,in a manner that the time information is compressed into the compressedtime information.

(30)

A transmission method including:

generating a physical layer frame in which a time informationdescriptor, which includes a time information flag which indicatespresence or absence of time information indicating a time of apredetermined position in a stream of the physical layer frame having apreamble and a payload and further includes the time information whenthe time information flag indicates the presence of the timeinformation, is included in the preamble; and

transmitting the physical layer frame.

(31)

A reception device including:

a reception unit configured to receive a physical layer frame in which atime information descriptor, which includes a time information flagwhich indicates presence or absence of time information indicating atime of a predetermined position in a stream of the physical layer framehaving a preamble and a payload and further includes the timeinformation when the time information flag indicates the presence of thetime information, is included in the preamble; and

a processing unit configured to perform a process using the timeinformation included in the time information descriptor included in thepreamble of the physical layer frame.

(32)

The reception device according to (31),

wherein the time information descriptor includes compressed timeinformation in which the time information is compressed.

(33)

The reception device according to (32),

wherein at least one low-order bit of the time information is deleted,in a manner that the time information is compressed into the compressedtime information.

(34)

The reception device according to (32) or (33),

wherein at least one high-order bit of the time information, thehigh-order bit having a value of 0, is deleted, in a manner that thetime information is compressed into the compressed time information.

(35)

The reception device according to any of (32) to (34),

wherein the time information descriptor further includes a compressionmode of the time information.

(36)

The reception device according to any of (31) to (35),

wherein the preamble has a first preamble and a second preamblecontinuously following the first preamble,

wherein the time information descriptor is included in the secondpreamble, and

wherein the time information included in the time information descriptorindicates a time of a position of a head of the second preamble.

(37)

The reception device according to any of (32) to (36),

wherein the time information is time information defined in Network TimeProtocol (NTP), time information defined in Third Generation PartnershipProject (3GPP), or time information defined in Precise Time Protocol(PTP).

(38)

The reception device according to (37),

wherein, in a 48-bit second field and a 32-bit nanosecond field includedin the time information defined in the PTP, at least one high-order bitof the second field is deleted and at least one low-order bit of thenanosecond field is deleted, in a manner that the time information iscompressed into the compressed time information.

(39)

The reception device according to (38),

wherein 2 high-order bits of the nanosecond field is further deleted, ina manner that the time information is compressed into the compressedtime information.

(40)

A reception method including:

receiving a physical layer frame in which a time information descriptor,which includes a time information flag which indicates presence orabsence of time information indicating a time of a predeterminedposition in a stream of the physical layer frame having a preamble and apayload and further includes the time information when the timeinformation flag indicates the presence of the time information, isincluded in the preamble; and

performing a process using the time information included in the timeinformation descriptor included in the preamble of the physical layerframe.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

REFERENCE SIGNS LIST

-   10 transmission device-   20 reception device-   30 transfer path-   61 time information acquisition unit-   62 descriptor generation unit-   63 preamble generation unit-   64 component acquisition unit-   65 encoder-   66 frame generation unit-   67 transmission unit-   68, 71 antenna-   72 tuner-   73 demodulation unit-   74 processing unit-   75 display unit-   76 speaker-   81 time information acquisition unit-   101 bus-   102 CPU-   103 ROM-   104 RAM-   105 hard disk-   106 output unit-   107 input unit-   108 communication unit-   109 drive-   110 input and output interface-   111 removable recording medium

The invention claimed is:
 1. A reception device comprising: a processorconfigured to: receive a physical layer frame including a bootstrap, apreamble, and a payload, wherein the preamble includes a timeinformation flag that indicates presence or absence of time informationin the physical layer frame, in a case where the time information flagindicates the presence of the time information, the time informationindicates a time at a head of the bootstrap, which is adjacent to thepreamble, and the time information is defined in accordance with aprecise time protocol.
 2. The reception device according to claim 1,wherein two bits are allocated to the time information flag.
 3. Thereception device according to claim 1, wherein, in a case where the timeinformation is present, the preamble includes information representativeof a precision of the time information.
 4. The reception deviceaccording to claim 1, wherein, in a case where the time information ispresent, a precision of the time information is a nanosecond or lessthan the nanosecond.
 5. The reception device according to claim 1,wherein, in a case where the time information is present, the timeinformation includes a 32-bit second field.
 6. The reception deviceaccording to claim 1, wherein the processor is configured to process thetime information and to control a timing of presentation of an image andaudio, the reception device includes a display and a speaker, and theimage is supplied to the display and the audio is supplied to thespeaker in accordance with the time information.
 7. The reception deviceaccording to claim 1, wherein the precise time protocol is defined by astandard belonging to: IEEE1588, 3GPP, third Generation PartnershipProject, NTP, Network Time Protocol, or GPS, Global Positioning System.8. The reception device according to claim 5, wherein the 32-bit secondfield includes 32 least significant bits of a number of seconds elapsedbetween the time at the head of the bootstrap and a second time.
 9. Thereception device according to claim 7, wherein the processor isconfigured to restore a time relative to a Precision Time Protocol epochusing the 32-bit second field.
 10. A reception method of a receptiondevice, the method comprising: receiving, by a processor of thereception device, a physical layer frame including a bootstrap, apreamble, and a payload, wherein the preamble includes a timeinformation flag that indicates presence or absence of time informationin the physical layer frame, in a case where the time information flagindicates the presence of the time information, the time informationindicates a time at a head of the bootstrap, which is adjacent to thepreamble, and the time information is defined in accordance with aprecise time protocol.
 11. The reception method according to claim 10,wherein two bits are allocated to the time information flag.
 12. Thereception method according to claim 10, wherein, in a case where thetime information is present, the preamble includes informationrepresentative of a precision of the time information.
 13. The receptionmethod according to claim 10, wherein, in a case where the timeinformation is present, a precision of the time information is ananosecond or less than the nanosecond.
 14. The reception methodaccording to claim 10, wherein, in a case where the time information ispresent, the time information includes a 32-bit second field.
 15. Thereception method according to claim 10, further comprising processingthe time information; controlling a timing of presentation of an imageand audio; and displaying the image on a display and outputting theaudio on a speaker in accordance with the time information.
 16. Thereception method according to claim 10, wherein the precise timeprotocol is defined by a standard belonging to: IEEE1588, 3GPP, thirdGeneration Partnership Project, NTP, Network Time Protocol, or GPS,Global Positioning System.
 17. The reception method according to claim14, wherein the 32-bit second field includes 32 least significant bitsof a number of seconds elapsed between the time at the head of thebootstrap and a second time.
 18. The reception method according to claim17, further comprising restoring a time relative to a Precision TimeProtocol epoch using the 32-bit second field.
 19. A reception devicecomprising: a tuner configured to receive a physical layer frameincluding a bootstrap, a preamble, and a payload, wherein the preambleincludes a time information flag that indicates presence or absence oftime information in the physical layer frame, in a case where the timeinformation flag indicates the presence of the time information, thetime information indicates a time at a head of the bootstrap, which isadjacent to the preamble, and the time information is defined inaccordance with a precise time protocol.
 20. The reception deviceaccording to claim 19, further comprising: a processing unit configuredto process the time information and to control a timing of presentationof an image and audio; a display; and a speaker, wherein the image issupplied to the display and the audio is supplied to the speaker inaccordance with the time information.
 21. The reception device accordingto claim 19, wherein the physical layer frame is an ATSC 3.0 physicallayer frame.
 22. The reception device according to claim 19, wherein theprecise time protocol is defined by a standard belonging to: IEEE1588,3GPP, third Generation Partnership Project, NTP, Network Time Protocol,or GPS, Global Positioning System.